Bi amping question

@peterb999 - connect the cables to the top posts and then placing your finger lightly on the bass driver cone check the bass driver for movement (i.e. if the grill can be removed)

Your speakers may be designed such that only the very low end of audio spetrum  is handled by the bass driver. and mid/upper bass frequencies are handled adequately by the other drivers.

If your music only has "mid bass" frequencies it might sound as though the bass driver is still connected.

Hope that helps 

Regards - Steve

http://imgur.com/gallery/Cx6bSfa
These are those speakers. They are 3way.
They definitely play full range when hooked up to upper posts as the bass speaker is moving and low bass are present.
Thanks

@mental Maybe... So does anybody know if it's safe to bi-amp in this case? I thought upper posts would drive only mids/highs which isn't the case. Curiously lower posts drive only bass section :/

Use a VOM to check the resistance between the two sets of posts.  If they aren't isolated from each other you don't want to try biamping as the two amps will interact.

For future reference, it was possible to biamp these speakers. Posts are wired so that the hidden speaker is connected to one binding post and rest of speakers to second binding post.
So basically williewonka was right.
Thanks all